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  Subjects -> ENGINEERING (Total: 2270 journals)
    - CHEMICAL ENGINEERING (191 journals)
    - CIVIL ENGINEERING (183 journals)
    - ELECTRICAL ENGINEERING (99 journals)
    - ENGINEERING (1199 journals)
    - ENGINEERING MECHANICS AND MATERIALS (390 journals)
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CHEMICAL ENGINEERING (191 journals)                     

Showing 1 - 191 of 191 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 6)
ACS Sustainable Chemistry & Engineering     Hybrid Journal   (Followers: 5)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 5)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Advanced Chemical Engineering Research     Open Access   (Followers: 30)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 5)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 8)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 15)
Biofuel Research Journal     Open Access   (Followers: 4)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 7)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
Chemical and Engineering News     Free   (Followers: 12)
Chemical and Materials Engineering     Open Access   (Followers: 12)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 12)
Chemical and Process Engineering     Open Access   (Followers: 26)
Chemical and Process Engineering Research     Open Access   (Followers: 23)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 32)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 18)
Chemical Engineering and Science     Open Access   (Followers: 18)
Chemical Engineering Communications     Hybrid Journal   (Followers: 14)
Chemical Engineering Education     Full-text available via subscription  
Chemical Engineering Journal     Hybrid Journal   (Followers: 33)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Engineering Research Bulletin     Open Access   (Followers: 11)
Chemical Engineering Science     Hybrid Journal   (Followers: 24)
Chemical Geology     Hybrid Journal   (Followers: 18)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 165)
Chemical Society Reviews     Full-text available via subscription   (Followers: 41)
Chemical Technology     Open Access   (Followers: 15)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry of Materials     Full-text available via subscription   (Followers: 189)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 4)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 20)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 6)
Current Opinion in Chemical Engineering     Open Access   (Followers: 7)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription   (Followers: 2)
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 6)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 2)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Heat Exchangers     Open Access   (Followers: 3)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 10)
Indonesian Journal of Chemical Science     Open Access   (Followers: 1)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 11)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 21)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 3)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access   (Followers: 1)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 3)
International Journal of Waste Resources     Open Access   (Followers: 4)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 5)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 6)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 12)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 117)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription   (Followers: 1)
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 6)
Journal of Chemical Engineering     Open Access   (Followers: 19)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Combinatorial Chemistry     Full-text available via subscription  
Journal of Crystallization Process and Technology     Open Access   (Followers: 8)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 5)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access   (Followers: 1)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal   (Followers: 1)
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 9)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 6)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 8)
Journal of Organic Semiconductors     Open Access   (Followers: 5)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 5)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 9)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 6)
Journal of Polymers     Open Access   (Followers: 5)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 292)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 5)
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Konversi     Open Access  
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 15)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
Nanochemistry Research     Open Access  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 4)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 4)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 2)
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 116)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 15)
Polyolefins Journal     Open Access  
Powder Technology     Hybrid Journal   (Followers: 13)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 60)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 4)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 2)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [24 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3031 journals]
  • Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for
           NH3-SCR (II): The impact of copper loading
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Jiaojiao Tang, Minhong Xu, Tie Yu, Hongfei Ma, Meiqing Shen, Jun Wang
      Four Cu/SAPO-34 samples by one-pot method are utilized to examine their durability after 950°C hydrothermal treatment and its relation with copper loading. The SCR results show fresh Cu/SAPO-34 with 3.91% copper loading (F-Cu-3.91) performs the superior NO conversion, wide temperature window and excellent nitrogen selectivity among fresh samples, and NO conversion is mainly determined by isolated Cu2+ contents at low temperature. After 950°C aging treatment, Cu/SAPO-34 catalysts with copper loading under 1.70% present good stability, while the ones with copper loading above 3.91% show activity and crystallinity decline. Ex-situ DRIFTs, XRD and NH3-TPD results reveal the 950°C aging process leads to Si-OH-Al bonds breakage and phase transition of chabazite support over Cu/SAPO-34 samples with high copper loading, meanwhile, the EPR and TPR outcomes prove the copper oxides’ further dispersion and coordination variation due to skeleton collapse. Finally, this work is trying to manifest the appropriate copper loading for a stable Cu/SAPO-34 catalyst and its deactivation mechanism during extreme working situation.
      Graphical abstract image

      PubDate: 2017-05-21T15:51:45Z
       
  • Influence of soot on ammonia adsorption and catalytic DeNOx-properties of
           diesel particulate filters coated with SCR-catalysts
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Marcus Purfürst, Sergej Naumov, Kay-Jochen Langeheinecke, Roger Gläser
      The effect of soot on the ammonia adsorption and the catalytic properties of a diesel particulate filter coated with a catalyst for the selective catalytic reduction of NO with ammonia (SDPF) was studied by means of model-gas experiments. After loading of the SDPF with model soot from 0 to 10gl−1, the NH3 storage as well as the catalytic DeNOx behavior in the standard SCR reaction was studied at temperatures between 423 and 673K for a gas hourly space velocity of 40.000h−1. In the presence of soot, less NH3 is adsorbed as shown by a breakthrough which occurs at earlier times-on-stream than in the absence of soot. Furthermore, the NO conversion on a soot-loaded SDPF is lower by up to 20% with respect to a soot-free SDPF. A 1-D microscopic filter wall model is presented. It contains the soot distribution along the filter wall, a kinetic SCR model and diffusive mass transfer of species through the wall-trapped soot. The soot inside the porous wall close to the zeolitic washcoat acts as a diffusive barrier, i.e., mass transfer through the soot is the rate-limiting process for the SCR reaction under the conditions studied. The model is also able to explain the NH3 storage behavior as well as the decrease of NO conversion in the standard SCR reaction for soot-free and soot-loaded SDPF. Also, a soot distribution with a high soot-coverage of the porous filter wall close to the inlet channel, a slightly covered middle part and a soot-free zone close to the outlet was derived from the model.
      Graphical abstract image

      PubDate: 2017-05-21T15:51:45Z
       
  • Effect of monoethylene glycol and kinetic hydrate inhibitor on hydrate
           blockage formation during cold restart operation
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Young Hoon Sohn, Yutaek Seo
      Hydrate blockage formation in offshore flowlines may induce production stoppage and operational hazards. Previous work suggested the risk of hydrate blockage became highest for water and decane mixture with 60% watercut, however the risk could be alleviated by adding a thermodynamic inhibitor along with the kinetic hydrate inhibitor. This work presents the effect of adding the hydrate inhibitors on hydrate blockage formation during cold restart operation, where the water and decane mixture stayed inside the hydrate formation region without mixing for 10h then executed mixing at constant stirring rates of 200, 400, and 600rpm. Depending on the mixing rate, liquid phase became stratified (200rpm), partial dispersing (400rpm), and full dispersing (600rpm). Without hydrate inhibitors, hydrates formed instantly upon mixing of liquid phase with fast growth rate. The stirrer was eventually stopped due to the formation of hydrate blockage within 13.9, 18.8, and 42.2min for stratified, partial dispersing, and full dispersing liquid phase, respectively. The resistance-to-flow could be estimated from the measurement of torque changes during the hydrate formation. Sever torque spikes were observed for the water and decane mixture without hydrate inhibitors. The hydrate growth rate decreases linearly as a function of hydrate fraction in liquid phase, then it drops upon torque spikes, possibly due to agglomeration and bedding of hydrate particles. Adding 20wt% mono-ethylene glycol (MEG) to the water phase could suppress the torque spikes while hydrate formation proceeds to the final fraction, suggesting MEG may prevent the agglomeration and bedding of hydrate particles for all flow regimes. However its performance was limited at 10wt% MEG concentration. The presence of kinetic hydrate inhibitor, Luvicap, was also found effective to suppress the hydrate formation for 155.0min at mixing rate of 200rpm, however soon lost its efficacy with increasing mixing rate to 400 and 600rpm. These results suggested that the hydrate formation mechanism during cold restart would be highly dictated by the mixing rate and corresponding flow regime, thus appropriate hydrate inhibition strategy must be developed to manage its risk. For 10wt%MEG and 0.1wt% Luvicap solution, hydrate formation initiated in interface between water and decane, then proceeded to gas phase without affecting the resistance-to-flow. The performance of hydrate inhibitors must be evaluated based on relevant data measurement and visual observation to better describe the hydrate formation mechanism.

      PubDate: 2017-05-21T15:51:45Z
       
  • Exploring the structure-property relationships of covalent organic
           frameworks for noble gas separations
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Minman Tong, Youshi Lan, Qingyuan Yang, Chongli Zhong
      In this work, a computation-ready, experimental covalent organic framework (CoRE COF) database that nearly covers all the existing COFs was constructed and provided, which contains 187 COFs with disorder-free and solvent-free structures. Using the CoRE COF database established, structure-property relationships of COFs for Kr/Ar, Xe/Kr and Rn/Xe separations were studied. The conditions of industrial vacuum (VSA) and pressure swing adsorption (PSA) processes were considered in the computation. Qualitative rules of COFs for noble gas separations were clarified, and structural features of COFs with excellent separation performance were summarized and suggested. In addition, COFs with good separation performance were identified from our database for industrial cyclic process. The knowledge obtained in this work may give guidance for experimental efforts in seeking advanced materials for noble gas separation, and the CoRE COF database will facilitate the fundamental research of COFs as well as the development of novel functional materials toward practical applications.
      Graphical abstract image

      PubDate: 2017-05-21T15:51:45Z
       
  • The establishment of a coke-burn kinetic model for zeolite catalysts
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Martin Dan Palis Søerensen
      The regeneration of coked samples of methanol-to-gasoline (MTG) catalyst applied in the commercial TIGAS (Topsoe Improved GAsoline Synthesis) process was studied by kinetic investigations of the coke-burn rate from temperature programmed oxidation (TPO) analysis of coked catalyst from a pilot plant reactor. The spent catalyst was unloaded, and samples covering the catalyst bed from reactor inlet to exit were analyzed by means of TPO. A rigorous kinetic model was fitted to the measured evolutions of CO2 and CO at the different catalyst bed heights. It was found that the diversity in oxidation reactivity of the coke observed along the axial reactor coordinate could be represented by lumping the various coke species into families characterized by having approximate the same oxidation reactivity. It was found that seven coke families were needed in order to obtain a satisfactory fit of the measured evolutions of CO and CO2. These seven coke families can roughly be divided into two categories; low-temperature (reactive) and high-temperature (less reactive) coke. Model testing is accomplished by applying the model to reconstruct a complete catalyst regeneration performed in situ in the pilot reactor. Model application illustrates that during the first step in an industrial regeneration, there is a risk of obtaining temperature excursions much higher than those expected, due to a combination of the amount of coke combusted as well as the cokes deposition along the catalyst bed length.

      PubDate: 2017-05-21T15:51:45Z
       
  • The role of interfacial tension in colloid retention and remobilization
           during two-phase flow in a polydimethylsiloxane micro-model
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Qiulan Zhang, S. Majid Hassanizadeh
      The work presented here consisted of steady-state and transient two-phase flow experiments on the role of interfacial tension in colloid transport. Experiments were performed in a polydimethylsiloxane (PDMS) micro-model containing a network of pores with a mean pore size of 30µm. The flow network covered an area of 1mm×10mm. Water and Fluorinert FC43 were used as the two immiscible liquids. Since PDMS is a hydrophobic material, Fluorinert was the wetting phase, and water was the non-wetting phase in this micro-model. The interfacial tension was changed by adding a Fluorinert-soluble surfactant into Fluorinert FC43 to change the interfacial tension from 55mN/m to 30mN/m. The colloids were fluorescent carboxylate-modified polystyrene microspheres and 300nm in diameter. We directly observed colloid movement using confocal microscopy. We also obtained colloid concentration breakthrough curves by measuring the fluorescent intensities in the outlet of the micro-model. The breakthrough curves showed that during steady-state unsaturated flow, fewer colloids were retained in the system when interfacial tension was lower. During transient flow, more colloids were remobilized by the moving Fluorinert-water interfaces (FWIs) and Fluorinert-water-solid contact lines (FWSCs) under high interfacial tension. Visualization results showed that, at low interfacial tension, the fluid-fluid interfaces were almost flat; thus, less interfacial area was available for colloid attachment. Generally, confocal images and measured breakthrough curves clearly demonstrate the effect of interfacial tension on colloid retention and remobilization.

      PubDate: 2017-05-21T15:51:45Z
       
  • Improved latent variable models for nonlinear and dynamic process
           monitoring
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Hongyang Yu, Faisal Khan
      The kernel mapping is a popular method for designing nonlinear process monitoring techniques. In most cases, kernel mapping is achieved by using the radial basis kernel function which, in theory, is able to provide an infinite order nonlinear mapping. However, such an infinite order mapping might be redundant and inefficient as the order of nonlinear relationship between process variables of industrial process system is often limited by many physical constraints. To address this issue, an efficient nonlinear mapping method called the constructive polynomial mapping (CPM) is utilized in lieu of the radial basis kernel function to avoid the excessive modeling redundancy. In addition, the CPM is integrated with the dynamic principal component analysis and the linear Gaussian state space model to build improved latent variable models for nonlinear and dynamic process monitoring. The promising performance of the proposed models has been demonstrated through two case studies.

      PubDate: 2017-05-16T12:17:22Z
       
  • Electrospun nanofiber of cobalt titanate perovskite as an enhanced
           heterogeneous catalyst for activating peroxymonosulfate in water
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Kun-Yi Andrew Lin, Tien-Yu Lin, Yi-Chun Lu, Jyun-Ting Lin, Yi-Feng Lin
      As perovskite-type metal oxides are attractive catalysts for activating peroxymonosulfate (PMS), cobalt titanate (CoTiO3 (CTO)) is particularly promising as CTO consists of earth-abundant Ti and Co is the most effective metal for PMS activation. However, conventional preparation methods of CTO result in large CTO aggregates, leading to very low surface area and porosity, and also limiting its performance. In the present study, an electrospinning technique is employed to prepare CTO nanoscale fiber (CTONF), which can exhibit a consistent nanoscale fibrous morphology, enabling CTO to exhibit a relatively large surface area and porosity, as well as mesoporous structures. Thus, CTONF shows a higher catalytic activity than the bulk CTO for activating PMS to degrade a model toxicant, Amaranth (AR) dye. The PMS activation behaviors are further investigated by examining the effects of temperature, pH, and NaCl on AR degradation by CTONF-activated PMS (CTONF-PMS). Through the effects of probe reagents, the AR degradation mechanism can be attributed primarily to sulfate radicals and hydroxyl radicals to a lesser extent. CTONF was also proven to activate PMS over multiple cycles without regeneration. These results reveal that CTONF is a high effective and recyclable heterogeneous catalyst for PMS activation as it outperforms the conventional bulk CTO. The findings obtained in this study also demonstrate that the electrospinning technique can be utilized to prepare perovskites with enhanced physical and chemical properties for catalytic advanced oxidation applications.
      Graphical abstract image

      PubDate: 2017-05-16T12:17:22Z
       
  • Summary of frictional drag coefficient relationships for spheres: Evolving
           solution strategies applied to an old problem
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Carlos A. Ramírez
      In 1851 Stokes reported his analytical solution for the kinetic force (form drag plus frictional drag) exerted by an unbounded fluid on a steadily falling sphere under very slow or creeping flow conditions. This so called Stokes’ law was improved in the early 20th Century by several authors, who included diverse approximations to the inertia term neglected by Stokes in the Navier-Stokes equation describing Newtonian fluid motion around the sphere. Lapple and Shepherd (1940) followed this fundamental theoretical work with a landmark plot relating the experimental frictional drag coefficient f (directly proportional to the kinetic force) to the sphere diameter-based Reynolds number (Re) for 0.1≤ Re ≤3.0E+06. Researchers quickly realized that Stokes’ law (valid for Re <0.1) was insufficient to explain the data over the entire span of Re, giving rise to new solution methodologies to predict f(Re). This communication gives a chronological listing of well-known f(Re) relationships, providing insights on the rationale and strategies used in their development. The modern chemical engineer can therefore readily assess the evolution of this problem and realize the remaining research gaps in the field of fluid flow around submerged spheres.
      Graphical abstract image

      PubDate: 2017-05-16T12:17:22Z
       
  • Methane hydrate reformation in porous media with methane migration
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Pengfei Wang, Mingjun Yang, Bingbing Chen, Yuechao Zhao, Jiafei Zhao, Yongchen Song
      The hydrate reformation that occurs in natural gas hydrate (NGH) exploration reduces mining efficiency and safety. To elucidate the hydrate formation/reformation characteristics during NGH exploration, methane hydrate (MH) was formed/reformed in two different modes to simulate mining of NGH sediment. The effects of residual water, residual MH and methane flow rate on MH reformation in a porous medium were investigated experimentally. Magnetic resonance imaging (MRI) was used to analyze MH saturation and distribution in the porous medium. In reformation, a positive correlation exists between the hydrate saturation (Sh) increment and MH dissociation. Moreover, the percentage of reformation Sh increment increases with the methane injection rate. That demonstrates MH dissociation by depressurization improves the contact area of gas-liquid and enhance the nucleation rate, which contributes to hydrate reformation. In addition, the residual Sw and MH reformation rate maximum (Rmax) are positively correlated in the rapid-reformation period. According to MRI images, crack-like pathways exist in the porous medium after MH dissociates completely in the first experimental mode. However, constantly flowing methane in the MH reformation process can render the water distribution uniform after MH dissociation in the second experimental mode. That means the methane flow affects the capillary force distribution then further influences the pore water distribution in porous medium.
      Graphical abstract image

      PubDate: 2017-05-16T12:17:22Z
       
  • Identification of flow regime in a cocurrent gas – Liquid upflow moving
           packed bed reactor using gamma ray densitometry
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Ali Toukan, Vineet Alexander, Hamza AlBazzaz, Muthanna H. Al-Dahhan
      Flow regime identification in upflow moving packed bed reactors with the conical bottom was investigated using non-invasive gamma-ray densitometry (GRD) measurement technique. Time domain (Standard Deviation), and state space or chaotic methods (Kolmogorov Entropy) are employed on photon count time series of GRD to determine flow regime. The experiments were performed on a pilot plant scale upflow packed bed reactor made of Plexiglas column of 27.94cm I.D and a total height of 118cm including plena, and it is packed randomly with 0.3cm diameter catalyst till 79cm including the conical bottom. Two axial and various radial position are selected to conduct GRD scanning. The measurements are conducted at superficial liquid (water) velocity 0.017cm/s and superficial gas (air) velocity in the range of 0.6–7.7cm/s under these conditions catalyst bed behaves as packed bed. All analysis showed similar flow regime trend, with observed flow regime as bubbly and pulse flow, when compared with flow regime map for upflow packed bed.

      PubDate: 2017-05-16T12:17:22Z
       
  • Analytical solutions for the free-draining flow of a Carreau-Yasuda fluid
           on a vertical plate
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Juan Manuel Peralta, Bárbara E. Meza, Susana E. Zorrilla
      Free-draining flow is observed in many practical and industrial situations. It is considered as a stage of a batch dip-coating process, where the draining of the fluid will form a liquid film over a substrate by gravity. The objective of this work was to develop a mathematical model and to obtain analytical solutions for the fluid-dynamic variables of a free-draining flow during a dip-coating draining stage of a finite vertical plate using a fluid whose rheological behavior is described by the Carreau-Yasuda model. Mathematical expressions have been obtained assuming a monophasic, isothermal, and nonevaporative system, where the most important forces are viscous and gravitational. The studied phenomena occurred far away from the meniscus formed at the surface of the fluid reservoir. The main operative variables that were estimated are velocity profile, flow rate, local thickness, and average thickness of the film. A validation was performed by using experimental data of average film thickness values of several representative food-grade fluids with coating capacity (emulsions and suspensions) obtained from the literature. The information published in this work will be useful for researchers and technicians to control and predict film characteristics (thickness and uniformity) and operational variables (velocity and flow rate) during laboratory and industrial coating processes where free-draining flow takes place.
      Graphical abstract image

      PubDate: 2017-05-16T12:17:22Z
       
  • Void fraction, bubble size and interfacial area measurements in co-current
           downflow bubble column reactor with microbubble dispersion
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Freddy Hernandez-Alvarado, Dinesh V. Kalaga, Damon Turney, Sanjoy Banerjee, Jyeshtharaj B. Joshi, Masahiro Kawaji
      Microbubbles dispersed in bubble column reactors have received great interest in recent years, due to their small size, stability, high gas-liquid interfacial area concentrations and longer residence times. The high gas-liquid interfacial area concentrations lead to high mass transfer rates compared to conventional bubble column reactors. In the present work, experiments have been performed in a downflow bubble column reactor with microbubbles generated and dispersed by a novel mechanism to determine the gas-liquid interfacial area concentrations by measuring the void fraction and bubble size distributions. Gamma-ray densitometry has been employed to determine the axial and radial distributions of void fraction and a high speed camera equipped with a borescope is used to measure the axial and radial variations of bubble sizes. Also, the effects of superficial gas and liquid velocities on the two-phase flow characteristics have been investigated. Further, reconstruction techniques of the radial void fraction profiles from the gamma densitometry's chordal void fraction measurements are discussed and compared for a bubble column reactor with dispersed microbubbles. Empirical correlations are also proposed to predict the Sauter mean bubble diameter. The results demonstrate that the new bubble generation technique offers high interfacial area concentrations (1000–4500 m2/m3) with sub-millimeter bubbles (500–900µm) and high overall void fractions (10–60%) in comparison with previous bubble column reactor designs.

      PubDate: 2017-05-16T12:17:22Z
       
  • [O]-induced reactive adsorptive desulfurization of liquid fuel over
           AgXO@SBA-15 under ambient conditions
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Feiyan Ye, Guang Miao, Liqiong Wu, Ying Wu, Zhong Li, Chunshan Song, Jing Xiao
      The development of processes for clean energy production with low energy consumption is a central strategy for a sustainable and environmentally friendly planet. Here we report a novel [O]-induced reactive adsorptive desulfurization (RADS) approach for ultra-clean fuel production using multifunctional AgXO@SBA-15 adsorbent with and without the addition of air under ambient conditions. The adsorption capacity of AgXO@SBA-15 by RADS reached 4.4 times of that by conventional ADS from low-sulfur fuel (10ppm-S), and its adsorption selectivity was enhanced 2.4 orders of magnitude. Over 90% of sulfur was removed within 10min (corresponds to the space velocity of 6h−1). The RADS mechanism was illustrated as a simultaneous oxidation of thiophenic compounds (to sulfones) and the selective adsorption of sulfones, where the nano-sized silver species detected at different valence states (AgO, Ag2O and Ag) and the fed air played the versatile enabling roles as the oxidation catalyst and the oxidant, respectively, and the surface silanol groups were suggested as the preferential adsorption sites for the sulfones yielded. The work may open up new avenues for developing supported metal oxides for ultra-clean fuel production under ambient conditions, taking advantage of self-retained [O] and/or introduced earth-abundant air.
      Graphical abstract image

      PubDate: 2017-05-12T07:27:33Z
       
  • An explicit adaptive grid approach for the numerical solution of the
           population balance equation
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Fabian Sewerin, Stelios Rigopoulos
      Many engineering applications, such as the formation of soot in hydrocarbon combustion or the precipitation of nanoparticles from aqueous solutions, encompass a polydispersed particulate phase that is immersed in a reacting carrier flow. From a Eulerian perspective, the evolution of the particulate phase both in physical and in particle property space can be described by the population balance equation (PBE). In this article, we present an explicit solution-adaptive numerical scheme for discretizing the spatially inhomogeneous and unsteady PBE along a one-dimensional particle property space. This scheme is based on a space and time dependent coordinate transformation which redistributes resolution in particle property space according to the shapes of recent solutions for the particle property distribution. In particular, the coordinate transformation is marched in time explicitly. In comparison to many existing moving or adaptive grid approaches, this has the advantage that the semi-discrete PBE does not need to be solved in conjunction with an additional system of equations governing the movement of nodes in particle property space. By design, our adaptive grid technique is able to accurately capture sharp features such as peaks or near-discontinuities, while maintaining the semi-discrete system size and adhering to a uniform fixed grid discretization in transformed particle property space. This is particularly advantageous if the PBE is combined with a spatially and temporally fully resolved flow model and a standard Eulerian solution scheme is applied in physical space. In order to accommodate localized source terms and to control the grid stretching, we develop a robust scheme for modifying the coordinate transformation such that constraints on the resolution in physical particle property space are obeyed. As an example, we consider the precipitation of BaSO4 particles from an aqueous solution in a plug flow reactor. Our findings demonstrate that for a given accuracy of the numerical solution the explicit adaptive grid technique requires over an order of magnitude fewer grid points than a comparable fixed grid discretization scheme.

      PubDate: 2017-05-12T07:27:33Z
       
  • Design of equipment modules for flexibility
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Heiko Radatz, Johannes Martin Elischewski, Matthias Heitmann, Gerhard Schembecker, Christian Bramsiepe
      A modular production plant consists of predefined apparatuses with a fixed design, called equipment modules. Selecting the equipment module with the appropriate suitable capacity to compensate fluctuations in production rate is one of the key challenges in module-based plant design. The equipment module’s operating window needs to fit and determines the point in time when a capacity expansion is required so that the operating window of the equipment module also affects a capacity expansion strategy. In order to avoid an unnecessary use of multiple apparatuses in parallel, equipment modules should be developed specifically for a large operating window in contrast to conventionally designed equipment. Therefore, an approach is required to design equipment modules for flexibility in production rate. In this work a method to design equipment modules for flexibility based on a global sensitivity analysis and the deduction of design rules of thumb is introduced. This method is applied to the design of a liquid/liquid heat exchanger without phase change. The resulting design for flexibility is compared to the conventional design with regard to the operating window and investment as well as operating costs. It is shown that for 14% higher annual costs a four-fold operating window can be obtained. This presents an important step towards increasing the competitiveness of modular production plants.

      PubDate: 2017-05-12T07:27:33Z
       
  • Thermodynamic modeling and uncertainty quantification of CO2-loaded
           aqueous MEA solutions
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Joshua C. Morgan, Anderson Soares Chinen, Benjamin Omell, Debangsu Bhattacharyya, Charles Tong, David C. Miller
      The accurate characterization of the thermodynamic models of a reactive solvent-based CO2 capture system is essential for adequately capturing system behavior in a process model. Moreover, uncertainty in these models can significantly affect simulation results, although it is often neglected. With this incentive, a model of thermodynamic properties, including vapor-liquid equilibrium (VLE), enthalpy, and solution chemistry, has been developed using a rigorous methodology for the aqueous monoethanolamine (MEA) system as a baseline. The final thermodynamic framework consists of both a deterministic and stochastic model. The deterministic model is developed by regressing parameters of the e-NRTL activity coefficient model in Aspen Plus® to VLE, heat capacity, and heat of absorption data while downselecting the model’s large parameter space through use of information-theoretic criteria. The stochastic model is developed through an uncertainty quantification (UQ) procedure, using the results of the deterministic regression to determine a prior parameter distribution. This prior distribution and the experimental VLE data are used to derive a posterior distribution through Bayesian inference, which is used to represent the final stochastic model. A reaction model in which the kinetics are written in terms of the reaction equilibrium constants, to ensure consistency with the thermodynamics model, is developed. These new thermodynamic and reaction models are incorporated into an existing MEA system process model from the open literature, and the prior and posterior parameter distributions are propagated through the models. This provides valuable insight into the extent to which uncertainty in thermodynamic models affects key process variables, including CO2 capture efficiency and energy requirement for solvent regeneration.

      PubDate: 2017-05-12T07:27:33Z
       
  • Comparison of gasification performances between raw and torrefied
           biomasses in an air-blown fluidized-bed gasifier
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Xiaoke Ku, Hanhui Jin, Jianzhong Lin
      A CFD-DEM model already developed by the authors has been extended to directly compare the gasification performances between raw and torrefied grassy biomasses in an air-blown fluidized-bed gasifier. The bed material is non-calcined olivine which acts as the solid heat carrier. Furthermore, effects of four key operating parameters (i.e., gasification temperature T r, excess air ratio λ, steam addition, and biomass feed location) are also systematically examined. The results are analyzed both qualitatively and quantitatively by various indices: the fluidization behavior, bed pressure drop, product gas concentration profiles, total gas yield, and carbon conversion (CC). For both raw and torrefied biomasses, increasing T r can enhance both the total gas yield and CC; rising λ decreases the H2 yield but increases the CO2 yield and CC; the steam addition has a positive influence on the total gas yield and CC and it can also be used to adjust the H2/CO ratio in the product gas; both the total gas yield and CC decrease with raising the height of the biomass feed location. For all cases, the torrefied biomass obtains a lower H2 yield and CC but a higher CO yield than its raw counterpart under the same operating conditions, suggesting that torrefied biomass requires a longer conversion process compared with raw fuel. Moreover, the gasification behavior of torrefied biomass is more dependent on the fuel feed location than raw fuel and such knowledge is important for the optimal design of fluidized-bed gasifier for torrefied feedstock.

      PubDate: 2017-05-12T07:27:33Z
       
  • The dependence of the phasic response of the taste nerves on stimulus flow
           rate arises in the diffusion boundary layer region at the lingual surface:
           A convective-diffusion analysis
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): John A. DeSimone
      The dynamics of the taste neural response are highly dependent on the velocity of the stimulus solution delivered to the taste receptor cells. In anesthetized rats, stimulus solution delivered at high stimulus flow rate (1 m1/s) to the taste receptor cells on the dorsal lingual surface by axisymmetric stagnation flow yields a neural response with a rapid transient increase above baseline to peak response. At flow cessation (after about 3s) the neural response then rapidly declines exponentially to steady state or tonic response. This rapid transient or phasic response is not observed at low stimulus flow rate (e.g. 7.5ml/min). In the latter case the neural response rises with a slow exponential decline ultimately attaining the same steady state value observed in the high flow rate case. Although the taste quality may be nominally the same in each case, the dynamics of the afferent response differ markedly. Therefore, the input to the brain, where a variety of sensory inputs related to food ingestion are combined to yield a food’s flavor value, is not the same for each flow rate. Thus physical variables at work in the oral cavity, such as flow velocity and viscosity, play a role in determining the palatability of a meal through their effects on both taste and tactile receptors. I show here that stimulus flow rate controls the appearance of a phasic transient neural response by its effect on the thickness of the diffusion boundary layer in contact with the dorsal lingual surface. This is accomplished by solving the convective-diffusion equation with the normal component of the stimulus flow velocity determined by stagnation flow fluid dynamics. In so doing I derive useful approximate closed form solutions for both planar and axisymmetric stagnation flow. I propose a mathematical model of taste receptor function that depends on the surface concentration of the taste stimulus. I show that the surface stimulus concentration (and therefore the neural response) increases with fluid velocity and that the thickness of the diffusion boundary layer is inversely proportional to the square-root of stimulus fluid velocity. A phasic transient neural response emerges at high flow rates because the surface stimulus concentration initially rises rapidly and then subsequently declines as the system evolves through a succession of steady states of diminishing fluid velocity. The model also accounts for diminished taste responses observed with increased stimulus solution viscosity.

      PubDate: 2017-05-12T07:27:33Z
       
  • Solid state foaming of poly(ethylene terephthalate) based on periodical
           CO2-renewing sorption process
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Tian Xia, Zhenhao Xi, Tao Liu, Ling Zhao
      The periodical CO2-renewing sorption process was applied in the solid state foaming of poly(ethylene terephthalate) (PET), in order to decrease the sorption time, increase the concentration of CO2 in PET matrix, and ultimately increase the expansion ratio of PET foams. The cell nucleation and growth were initiated after every depressurization in the sorption process, and the concentration of the dissolved CO2 was reduced by the consumption of cells nucleation and cells formation, which inhibited CO2-induced crystallization. As a result, the CO2 concentration of 150–160mg/g PET was obtained, which was much higher than the reported CO2 solubility in PET matrix (∼110mg/g PET). With different sorption temperatures and CO2-renewing periods, PET foams with the cell size between 5 and 22μm, the cell density between 2.42×108 and 2.93×109 cells/cm3, and the expansion ratio between 3 and 6 times were controllably prepared. Only 1h was required to enhance the crystallinity of PET foams to about 30% by the means of annealing treatment at 110–130°C. And the cell morphology was still well kept during the annealing process.

      PubDate: 2017-05-07T11:54:51Z
       
  • Optimal control of univariate and multivariate population balance systems
           involving external fines removal
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): S. Hofmann, N. Bajcinca, J. Raisch, K. Sundmacher
      We propose an algorithm for optimal control of univariate and multivariate population balance systems governed by a class of first-order linear partial differential equation of hyperbolic type involving size dependent particle growth and filtering. In particular, we investigate the impact of filtering on the optimal control outcomes. To this end, we apply a recently developed polynomial method of moments and a standard steepest descent gradient-based optimization scheme to batch crystallization benchmark problems involving external fines removal. Numerical evaluations for various case-studies aiming at minimizing the mass of grown nuclei in the context of crystal shape manipulation demonstrate the effectiveness of fines dissolution. We also validate the accuracy of the proposed method of moments by utilizing a known numerical moving grid discretization method as a reference. Our results are of interest for the control of a wide range of population balance systems in various applications such as pharmaceutics, chemical engineering, particle shape engineering.

      PubDate: 2017-05-07T11:54:51Z
       
  • Local transport and reaction rates in a fixed bed reactor tube:
           Endothermic steam methane reforming
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Anthony G. Dixon
      Resolved-particle 3-D computational fluid dynamics (CFD) simulations are presented of endothermic steam methane reforming in a random packed bed of 807 spherical catalyst particles at a tube-to-particle diameter ratio of N=5.96 with constant wall heat flux. The fluid flow field is fully coupled to the temperature and species distributions inside the particles. This enables simulation of diffusion, conduction and reaction inside the catalyst particles, as opposed to only surface reactions. The results illustrate 3-D distributions of flow, temperature, species and reaction rates inside a 0.7m length of packed tube. These show large variations on near-wall particle external surfaces, and non-symmetric distributions inside the catalyst particles on cross-sections through the bed. The detailed CFD approach allows statistical analysis of the particle-to-particle reaction rate variations, the correlation of rate with location in the bed, and the intrinsic variability of radial temperature and species mass fraction profiles. Comparisons to a 1-D reactor tube heterogeneous effective medium model showed that axial profiles of cross-sectional average temperature, species and velocity could not be reproduced using particle-fluid heat and mass transfer coefficients estimated from non-reacting simulations in the same tube. Comparisons to a 2-D reactor tube heterogeneous effective medium model showed good agreement with axial profiles if radial local void fractions and axial velocities were included in the model. Improved agreement with radial temperature profiles resulted from the model with a radially-varying effective radial thermal conductivity.

      PubDate: 2017-05-07T11:54:51Z
       
  • Kinetic modeling of carboxylation of propylene oxide to propylene
           carbonate using ion-exchange resin catalyst in a semi-batch slurry reactor
           
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Xin Jin, Pallavi Bobba, Nicolas Reding, Ziwei Song, Prem S. Thapa, Guru Prasad, Bala Subramaniam, Raghunath V. Chaudhari
      Kinetic modeling of carboxylation of propylene oxide with CO2 to propylene carbonate has been investigated in a semi-batch slurry reactor. Propylene oxide can be selectively transformed into propylene carbonate (selectivity: 99+%) in the presence of ion exchange resin catalysts with basic functional groups. The effect of reaction temperature (65–95°C), CO2 pressure (0.5–3.0MPa), propylene oxide concentration in propylene carbonate (as a solvent) on the carboxylation rates was studied. Experimental results show that CO2 displays inhibition effect on carboxylation reaction at high pressure conditions. For kinetic modeling, three types of rate models were investigated, including two involving Langmuir-Hinshelwood and one modified Eley-Rideal mechanisms. Details of model discrimination and evaluation of kinetic parameters are discussed. Based on the parameter estimation and rigorous model discrimination, it is found that the proposed modified Eley-Rideal rate model describing surface reaction between free PO and adsorbed CO2 on catalyst surface fits the experimental data very well.

      PubDate: 2017-05-07T11:54:51Z
       
  • A systematic investigation of the fouling induction phenomena with
           artificial crystal structures and distributions
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Jie Xiao, Zhihao Li, Jian Han, Fei Pan, Meng Wai Woo, Xiao Dong Chen
      It has been a challenge to understand the negative fouling resistance during the induction stage of many crystallization fouling processes. The evolution of complex fouling layer structure (i.e., mesoscale crystal structure) and its intricate interaction with heat and momentum transfer in a heat exchanger are extremely difficult to be rigorously tracked experimentally. In this work, a 3D computational fluid dynamics (CFD) model was developed for the induction stage of fouling in a microscale channel. The growth of crystals with artificially designed structures at the micrometer scale has been explicitly modeled and coupled with flow dynamics and heat transfer. This model offers unique opportunities to investigate a variety of crystal structures that include the density, distribution, shape, orientation, and growth schemes. Dominant mechanisms of heat transfer enhancement during the induction stage have been demonstrated by the quantification and analysis of Nusselt number ratios. Moreover, quantitative findings in this work can be used to guide the design of high-performance heat transfer facilities.
      Graphical abstract image

      PubDate: 2017-05-07T11:54:51Z
       
  • A new numerical method for axial dispersion characterization in
           microreactors
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Maxime Moreau, Nathalie Di Miceli Raimondi, Nathalie Le Sauze, Christophe Gourdon, Michel Cabassud
      Axial dispersion is a key phenomenon in reactor engineering that can affect yield and selectivity when reactions are carried out. Therefore its characterization is necessary for an adequate modelling of the reactor. The development of compact reactors to fit with process intensification expectations requires the use of characterization methods adapted to small-scale devices. An original method not-frequently used up to now for the estimation of axial dispersion coefficients is presented and applied to millimetric wavy channels. It is based on CFD simulations to calculate velocity and concentration fields from which axial dispersion coefficient can be estimated. This method is used to predict the impact of the wavy channel geometry and of the fluid velocity on axial dispersion in laminar flow regime. The investigated geometrical parameters are the hydraulic diameter (2–4mm), the cross-sectional aspect ratio defined as the ratio between the channel width and its depth (0.25–1) and the internal curvature radius of the bends (2–3.4mm). The range of Reynolds number considered is Re =70–1600. Axial dispersion coefficient increases with velocity, values range from 2.8·10−4 to 3.2·10−3 m2·s−1. It appears that axial dispersion varies slightly in function of the channel hydraulic diameter. Square wavy channels generate less axial dispersion than rectangular wavy ones. Finally, axial dispersion coefficient increases with the internal curvature radius which shows the positive impact of sharp bends to reduce axial dispersion effect.

      PubDate: 2017-05-07T11:54:51Z
       
  • Characterization of stability limits of Ledinegg instability and density
           wave oscillations for two-phase flow in natural circulation loops
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Vikas Pandey, Suneet Singh
      A detailed study of excursive (or Ledinegg) instability and density wave oscillations (DWOs) is carried out for two-phase flow in a natural circulation loop. The maps in the parametric space have been obtained, which indicate excursive instability (Ledinegg instability) as well as density wave oscillations (DWOs). The dynamic (DWOs) and static (Ledinegg) stability boundary on these maps have been drawn. These diagrams dealing with the interaction of Ledinegg instability and DWOs have rarely been reported, and detailed mathematical analysis of these maps is lacking. In the present work, a detailed study of such interactions is carried out. It is also noted that the Ledinegg instability is a manifestation of saddle node bifurcation or limit point (LP) for the dynamical system of natural circulation loop. Density wave oscillations in the dynamical system of natural circulation loop can be observed with the Hopf bifurcation. The detailed bifurcation analysis of these instabilities shows that stability maps can be divided into three broad regions, the first region can only have DWOs (Hopf bifurcation), and the second region can have Ledinegg as well as DWOs (Hopf bifurcation and saddle node bifurcation co-exists), while the third region can have only Ledinegg instability (saddle node bifurcation). The first and second region are separated by a Cusp point (CP) and it is found that between CP and Bogdanov-Takens (BT) bifurcation point both Hopf and LP exist, due to presence of both DWOs and Ledinegg instability. The region beyond BT bifurcation point only has Ledinegg or excursive instability. Moreover, DWOs in the first region have two types of Hopf bifurcation depending on the nature of limit cycles. These subcritical and supercritical Hopf bifurcations, are separated by the Generalized Hopf (GH) bifurcation. Abovementioned three regions are observed only for the Type II DWOs stability boundary, whereas Type I DWOs have only subcritical and supercritical Hopf bifurcations. The impact of design parameters on the saddle-node curve along with the shifting of interaction point (Bogdanov-Takens bifurcation) have been investigated as well.

      PubDate: 2017-05-07T11:54:51Z
       
  • Pre-reforming of higher hydrocarbons contained associated gas using a
           pressurized reactor with a Ni19.5-Ru0.05/CGO catalyst
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Seunghyeon Choi, Joongmyeon Bae, Sangho Lee, Jiwoo Oh, Sai P. Katikaneni
      In this paper, we investigated the use of Ni19.5-Ru0.05/CGO as catalysts for associated gas pre-reforming to convert higher hydrocarbon and obtain higher methane content. To increase the content of methane, we perform catalytic pre-reforming experiments at 8bars. Ni-Ru/CGO fully converted the C2–C5 hydrocarbons at 500°C. However, the conversion of C2–C5 hydrocarbons decreased from 100% to 80% as the SCR decreased from 3.0 to 1.0. Catalytic degradation occurred at temperatures below 300°C. Comparing the commercial pre-reforming catalyst (C11PR, produced by Süd-Chemie) with Ni-Ru/CGO catalysts, Ni-Ru/CGO outperformed C11PR under the same conditions. We performed long-term tests with Ni-Ru/CGO. Each long-term test lasted over 900h. Initially, the methane yield was approximately 60%, and the higher hydrocarbons were fully converted. After 900h, the methane yield was approximately 55%, and dramatically reaching to 50% at 920h. Simultaneously, the C2–C5 hydrocarbon yield increased to approximately 8%. After the long-term test, we analyzed the tested catalysts and determined that catalytic degradation occurred due to carbon deposition on the catalyst surface.

      PubDate: 2017-05-01T11:53:46Z
       
  • Experimental study and numerical simulation of periodic bubble formation
           at submerged micron-sized nozzles with constant gas flow rate
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Jian Zhang, Yong Yu, Chen Qu, Yu Zhang
      Visualization experiments and numerical simulations were carried out to investigate the bubble dynamic behavior at the submerged micron orifice. The diameters of the orifices varied from 0.136mm to 0.204mm. The bubble formation process was recorded by a high-speed video camera. The detailed bubble characteristics were obtained through image processing and a following Matlab analysis. The outcomes indicate that under a low gas flow rate, the bubble grows and detaches individually, and the bubble formation progress can be differentiated into three stages: nucleation, stable growth, and necking. The differences between micron and millimeter level orifices are obvious at the initial level of bubble formation. At the micron level, the bubble is strongly influenced by capillary pressure and it causes a longer waiting time. It is also found that the bubble shape only depends on the instantaneous bubble volume and has no relation with the gas flow under a high flow rate. We observed that the coalescence bubbling regimes are different from the multi-period formation mechanism at the millimeter level. The final bubble volume demonstrates an index increasing law with the gas flow rate. Additionally, the volume-of-fluid method was used for numerical simulation of the bubble formation process. It indicates that numerical simulations can finely predict the dynamic features of bubbles against the experiments, under low gas flow rate conditions (0.95–4.83ml/min).

      PubDate: 2017-05-01T11:53:46Z
       
  • Effect of granular temperature and solid concentration fluctuation on the
           gas-solid drag force: A CFD test
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Junwu Wang
      Recent studies have shown that the expanded bed heights of bubbling fluidized beds obtained from direct numerical simulations (DNS) are higher than those obtained from CFD-DEM method. In this study, we show that the consideration of the effect of either granular temperature using the model proposed by Tang et al. (AIChE Journal, 2016, 62: 1958–1969) or solid concentration fluctuation on the interphase drag force can significantly improve the agreement with the DNS results. This study highlights the importance of the fluctuation of state variables on the accurate CFD simulation of gas fluidization.

      PubDate: 2017-05-01T11:53:46Z
       
  • Hydrodynamics and mass transfer coefficients in a bubble column
           photo-bioreactor
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Onkar N. Manjrekar, Yujian Sun, Lian He, Yinjie J. Tang, Milorad P. Dudukovic
      The present study compares typical measurements of bubble dynamics obtained with a 4-point optical probe over the same range of superficial gas velocity in the same size gas–liquid contactor in two different systems. The classical bubble column (BC) arrangement employed air bubbled through water. The photo-bioreactor (PBR) used a growing algae in appropriate culture solution. Local gas holdup distribution across the vessel was monitored, as well as the local distribution of bubble velocity, bubble chord length, bubble frequency and interfacial area per unit volume for both systems. It was observed these parameters were significantly different in the photo-bioreactor. This information coupled with the tracer absorption studies with oxygen provided the needed information to evaluate the gas liquid volumetric mass transfer coefficients from an appropriate model for both systems. The development of such a model is described. It was concluded that the difference in hydrodynamics of the two systems was due to difference in physicochemical properties.

      PubDate: 2017-05-01T11:53:46Z
       
  • Degradation of methylene blue using double-chamber dielectric barrier
           discharge reactor under different carrier gases
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Baowei Wang, Bo Dong, Meng Xu, Chunmei Chi, Chao Wang
      The decomposition of methylene blue (MB) via a novel double-chamber dielectric barrier discharge (DBD) reactor in different carrier gases (air and oxygen) was investigated. The results showed that the degradation efficiency of MB was 99.98% using O2 plasma for 20min, while it was only 85.3% using air plasma for 100min. In addition, the concentrations of nitrite, nitrate, ozone and hydrogen peroxide in aqueous phase and the oxidizing ability of the oxidants were measured to explore the various results obtained in different carrier gases. The formation of nitrogenous species was considered to be the main reason for the low degradation efficiency of the air plasma. The accumulation of oxidants enhanced the degradation efficiency of the MB in the O2 plasma. Both the combined effects of ozonation and plasma with oxygen bubbling and the reaction poisoning with air bubbling were enhanced in the double-chamber DBD reactor. The decomposition routes of MB and byproducts formation were also proposed.
      Graphical abstract image

      PubDate: 2017-05-01T11:53:46Z
       
  • Whole-field imaging of temperature and hydrodynamics in a gas fluidized
           bed with liquid injection
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): T. Kolkman, M. van Sint Annaland, J.A.M. Kuipers
      This work presents results of experiments on thermal effects and flow dynamics in a flat-bed geometry gas-fluidized bed at atmospheric pressure, with and without liquid injection. Whole-field measurements have been performed using a combination of thermography, particle image velocimetry and digital image analysis. A first series of experiments demonstrates the mixing of two layers of particles at initially different temperature for a sequence of injected gas bubbles. It is shown that the pulse duration strongly affects the solids mixing and that the influence of diffusion on thermal equilibration is limited without convective mixing. Subsequently liquid has been injected into the fluidizing bed, which has been carried out with water, isopentane and hexane. Owing to the use of a combination of infrared and visual cameras, under particular conditions liquid-solid conglomerates can be observed in situ. Under the conditions applied, the flow dynamics are not clearly affected by the liquid injection. The thermal behavior of the bed is not found to be strongly dependent on which of the model liquids is injected, but more on the cooling capacity obtained by evaporating the injected amount of liquid at the selected injection rate, and the mode of operation.
      Graphical abstract image

      PubDate: 2017-05-01T11:53:46Z
       
  • Study of interaction pattern between bubbles at three inline orifices in a
           submerged pool
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Basanta Kumar Rana, Arup Kumar Das, Prasanta Kumar Das
      Experiments have been performed to study evolution and interaction of bubbles over three inline submerged orifices. Complete, partial and non-coalescence patterns are observed during the growth of bubbles at similar and dissimilar spacing and diameter of orifices. When orifices are equispaced and similar in size, symmetric interfacial shape is observed during coalescence, but unequal orifice spacing resulted in asymmetric merging of bubbles. Drainage of liquid before initiation of coalescence and growth of gaseous bridge between bubbles before unification are observed for both symmetric and asymmetric arrangements. Effect of gas flow rate has been observed for equal and unequal spacing. Delay in merge time is one of the important parameter which has been observed in case of unequal orifice spacing distances and its effect is analyzed for different air flow rate into the liquid tank. Scattered regime plot has been shown in order to understand the bubble coalescence and non-coalescence patterns in different zones and combinations of orifice sizes and orifices spacing.

      PubDate: 2017-05-01T11:53:46Z
       
  • Heat transfer performance assessment of hybrid nanofluids in a parallel
           channel under identical pumping power
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Chen Yang, Xiaowei Wu, Yongkun Zheng, Ting Qiu
      In the study, a mathematical model of hybrid nanofluids was established with the consideration of nanoparticles migration, which has significant influence on the thermophysical properties of hybrid nanofluids. In order to investigate heat transfer and friction factor characteristics of hybrid nanofluids in a channel, the corresponding governing equations were solved by using the Runge-Kutta-Gill method. A Performance Evaluation Criteria (PEC) was used to assess heat transfer performance of hybrid nanofluids under identical pumping power. Two hybrid nanofluids, which are alumina-titania/water nanofluid and alumina-zirconia/water nanofluid, respectively, were discussed. The results clearly indicated that alumina-titania/water nanofluid exhibits higher Nusselt number and lower friction factor than alumina-zirconia/water nanofluid. Moreover, it has been found that with the variation of volume fraction ratio of two single-particle nanofluids, maximum PEC values of alumina-titania/water nanofluid were observed, proving that alumina-titania/water nanofluid has better heat transfer performance than either alumina/water nanofluid or titania/water nanofluid under identical pumping power. The effects of N BT 1 variation and N BT 2 variation of alumina-titania/water nanofluid on Nusselt number and friction factor were also investigated. It is interesting to note that minimum PEC values were observed under the variation of N BT 2 whenN BT 1 / N BT 2 is approximately 6. However, maximum PEC values were observed under the variation of N BT 1 when N BT 1 / N BT 2 is approximately 0.5.

      PubDate: 2017-05-01T11:53:46Z
       
  • Mixing in oscillating columns: Experimental and numerical studies
    • Abstract: Publication date: 31 August 2017
      Source:Chemical Engineering Science, Volume 168
      Author(s): Shivkumar Bale, Kristopher Clavin, Mayur Sathe, Abdallah S. Berrouk, F. Carl Knopf, Krishnaswamy Nandakumar
      In this paper, mixing in an oscillating column was experimentally and numerically studied as a function of power applied through vibrations. The mixing experiments were performed using phenolphthalein and NaOH solution, and the mixing time was computed using a simple image processing algorithm to track intensity changes implemented in MATLAB. Numerically, the air-solution interface was tracked using the VOF model and the solution was vertically disturbed by oscillating the base of the column. The bottom boundary was treated as a rigid moving boundary and a compiled user-defined function (UDF) was applied to the boundary to impose a sinusoidal displacement of the lower boundary. The interior of the column was assumed to be a deforming body and a dynamic mesh was employed to improve the mesh quality. It was found that the mixing time is highly nonlinear with respect to the applied power. The stability chart mapped in Benjamin and Ursell (1954) by solving a series of Mathieu equations was applied to our system and the behavior of mixing in the vibrating column was interpreted. Pseudo steady states were observed, however they lasted only for few minutes and then switched back to ‘real’ steady states. These findings were supported by the images captured during experiments and numerically-produced iso-surface and contour plots.

      PubDate: 2017-05-01T11:53:46Z
       
  • Modeling and optimization of spherical agglomeration in suspension through
           a coupled population balance model
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Ramon Peña, Christopher L. Burcham, Daniel J. Jarmer, Doraiswami Ramkrishna, Zoltan K. Nagy
      The population balance model is the common approach to simulation and prediction of the size distribution and other properties of particulate systems. Population balance models include any nucleation, growth, breakage and agglomeration mechanisms that are relevant to all industrial particulate processes. However, there are some limitations to many of the previous population balance model formulations for systems with agglomeration. Limitations include physically irrelevant and/or empirically based agglomeration kernels, difficulties in assessing the influence of process conditions (e.g. hydrodynamics, particulate physical properties), solution method efficiency for optimization and control applications, and loss of information on constituent particles. These limitations have prevented the use of population balance models to accurately predict and simulate agglomeration in suspension techniques such as spherical crystallization. To overcome these limitations, an extension of the concept of a coupled population balance model is presented for application in the simulation and optimization of a spherical crystallization system. A coupled population balance model formulation has been developed for a semi-batch, reverse addition, anti-solvent crystallization system with agglomeration. The system includes nucleation and growth of the primary crystals and subsequent agglomeration. The advantages presented by a coupled population balance model formulation include the ability to optimize for specific primary and agglomerate sizes. This presents an opportunity to find optimal operating conditions that meet both bioavailability and manufacturability demands.

      PubDate: 2017-05-01T11:53:46Z
       
  • Freezing kinetics of vacuum-induced surface directional freezing in a
           glass vial
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Sandra Groβberger, Tobias Fey, Geoffrey Lee
      Directional freezing is used to prepare aligned porous materials made from ceramic dispersions. The alternate procedure of vacuum-induced surface-freezing uses a reduction in pressure to achieve freezing rather than the use of a cryogen-driven cold-finger. In this work the rate of directional freezing that occurs during vacuum-induced surface freezing of alumina dispersions in glass vials was measured using a video camera technique. The rate of advancement of the freezing front is broadly similar to that seen with conventional freeze casting: initially 900µm/s caused by spontaneous freezing of a surface layer at 250mTorr, followed by steady state at approximately 12–15µm/s during directional freezing. The steady state phase could be described by Stefan’s equation where the ice layer thickness grows with the square root of time. The temperature differences across the sample necessary to give the measured rates of advancement of the freezing front were calculated to be 18.8°C, 13.9°C and 9.1°C for volume fractions of dispersed phase of 0.032, 0.064 and 0.128, respectively. The temperature of the slurry below the freezing front declined from 0°C at the start of directional freezing to around −23°C at its conclusion. Stefan’s equation predicts that the temperature of the cold source, i.e. a sublimation front, is −14°C declining to −37°C, which are plausible values. The mechanism of vacuum-induced surface directional freezing is suggested to be undercooling of the slurry surface to below −10°C at reduced pressure by evaporative water loss. After rapid formation of a continuous, frozen surface-layer, sublimation starts and the enthalpy of sublimation assumes the role of a cold source for directional freezing. A sublimation front moves down through the frozen region behind the freezing front and has a rapidly declining temperature down to below −35°C. This is the cold source for directional freezing.

      PubDate: 2017-04-24T17:03:59Z
       
  • Spray drying of mixed amino acids: The effect of crystallization
           inhibition and humidity treatment on the particle formation
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Ruohui Lin, Meng W. Woo, Zhangxiong Wu, Wenjie Liu, Jisheng Ma, Xiao D. Chen, Cordelia Selomulya
      This study focused on the spray drying of mixtures of amino acids by systematically investigating the influence of crystallization inhibition between taurine and glycine on particle formation. Two well-controlled drying techniques, namely Single Droplet Drying (SDD) and Micro Fluidic Jet Spray Drying (MFJSD), were used. An extended nucleation time, compared to that of pure amino acid, was first observed in the mixed AA sample dried from SDD, possibly as a result of crystallization inhibition. The spray-dried particles were dense microspheres, compactly assembled by numerous fine crystal grains of uniformly distributed taurine and glycine. Crystallization inhibition was also confirmed by the presence of the unstable polymorphic form of glycine in the spray-dried mixed AA particles obtained from MFJSD, and was verified to be strongly associated to the formation of nanocrystals. The spray-dried microspheres were likely formed in a two-stage process of rapid nucleation followed by inhibited growths of taurine and glycine. The microstructure of mixed AA particles, assembled by nanometer-scale grains with the increasing size towards the inner particle, was due to the crystallization behavior of amino acids during convective drying. In the post-drying humidity treatment, a significant segregation between taurine and glycine was in a clear contrast to the uniform distribution in those without treatment. Such segregation was possibly be due to various solubilities of taurine and glycine and their recrystallization in the humid condition. The recrystallization mechanism was further validated by a real-time observation of the morphological evolution on the particle surface. To the best of our knowledge, this is the first work that captured in real time the effects of post-humidity treatment on the morphological differentiation in spray-dried mixed amino acid particles. The understanding obtained here would advance the design formulation of amino acid particles.
      Graphical abstract image

      PubDate: 2017-04-24T17:03:59Z
       
  • Experimental and theoretical analysis of TiO2 powders flow properties at
           ambient and high temperatures
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Domenico Macrì, Diego Barletta, Paola Lettieri, Massimo Poletto
      Changes of bulk flow properties of two different types of titanium dioxide powders are measured at room temperature and 500°C using the High Temperature Annular Shear Cell. A significant increase of the macroscopic bulk flow properties is observed with increasing temperature, in particular with regards to the unconfined yield strength. Two different modelling approaches are proposed with the aim to relate the measured properties to the microscopic interactions between particles. The results indicate that both the model provides a good match with the experimental data when proper values for the models’ parameters are taken into account. To this end, the sensitivity analysis for the main parameters of the models is performed.

      PubDate: 2017-04-24T17:03:59Z
       
  • Experimental measurements of particle collision dynamics in a pseudo-2D
           gas-solid fluidized bed
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Zhaochen Jiang, Thomas Hagemeier, Andreas Bück, Evangelos Tsotsas
      Based on particle tracking velocimetry (PTV) measurements by Hagemeier et al. (2014), the particle tracking approach is further optimized to accurately measure complex granular flows in a pseudo-2D fluidized bed. The particle granular temperature, particle collision frequency and impact velocity are systematically investigated under various operation conditions. Collision events are identified by a self-developed algorithm based on the variation of individual particle trajectories obtained from PTV measurements. The circulation pattern of particles in the fluidized bed can be well represented using the time-averaged volumetric flux of particles. The evaluation of granular temperature depends on the size of the investigation region. The value of granular temperature and the corresponding anisotropy significantly decrease as the size of the investigation region varies from 45 times particle diameter to 6 times particle diameter. Compared to the collision model of the kinetic theory of granular flow, the experimental collision frequency tends to be relatively constant or even decrease after exceeding a critical solid volume fraction. This is a result of competing contributions of increasing solid volume fraction and decreasing granular temperature. The average impact velocity correlates linearly with the average square root of granular temperature. The slope of this linear equation depends on the location within the fluidized bed.
      Graphical abstract image

      PubDate: 2017-04-24T17:03:59Z
       
  • Sequence editing strategy for improving performance of
           β-glucuronidase from Aspergillus terreus
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Yinghua Xu, Yanli Liu, Aamir Rasool, Wenwen E, Chun Li
      β-Glucuronidase from Aspergillus terreus Li-20 (AtGUS) can hydrolyze the glycyrrhizin (GL) into glycyrrhetinic acid 3-O-mono-β-d-glucuronide (GAMG) and glycyrrhetinic acid (GA). However, its low catalytic efficiency and thermal instability limit its application at industrial scale biotransformation of GL. In this work, sequence editing strategy was employed to improve the performance of AtGUS. Herein, three mutants, AtGUS-t1, AtGUS-t2 and AtGUS-t3 were constructed through partial truncation of the C-terminal non-conserved sequence of wild-type enzyme AtGUS based on the hydropathy profile and secondary structure of the C-terminal non-conserved. In addition, two more mutants were constructed by splicing of the C-terminal non-conserved sequence. The splicing mutant AtGUS(P) has a C-terminus consisting of merely polar amino acid residues with all non-polar amino acid residues knocked out from the C-terminal non-conserved sequence, consequently a highly hydrophilic C-terminus generated. Conversely, the other splicing mutant AtGUS(NP) has a C-terminus composed of merely non-polar amino acid residues, presenting a highly hydrophobic C-terminus. Among the truncated mutants, only the mutant AtGUS-t3 deleted a C-terminal hydrophilic coil peptide increased 3.8-fold catalytic efficiency with kcat /Km value of 8.31mM−1·s−1. The splicing mutant AtGUS(P) expanded the optimal pH range compared to the wild-type AtGUS and retained more than 80% relative activity in alkaline pH (pH 8.0). The another splicing mutant AtGUS(NP) displayed an increased thermal stability and conserved more than 50% relative activity at 65°C for 30min compared to AtGUS, which only held less than 20% relative activity under the same treatment condition. The results of this study demonstrate that sequence editing in truncation/splicing of C-terminal non-conserved region/residues could improve enzyme performance and is a potentially simple and efficient protein engineering strategy for the important industrial enzymes.
      Graphical abstract image

      PubDate: 2017-04-17T16:52:05Z
       
  • Quenched breathing effect, enhanced CO2 uptake and improved CO2/CH4
           selectivity of MIL-53(Cr)/graphene oxide composites
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Xin Zhou, Wenyu Huang, Jiang Liu, Haihui Wang, Zhong Li
      Compositing graphene oxide (GrO) as a robust support into MIL-53(Cr) can provide a feasible strategy to stabilize its flexible structure from CO2-triggered shrinkage, resulting in an enhanced CO2 uptake together with a higher CO2/CH4 adsorptive selectivity of the GrO@MIL-53(Cr) composites for biomethane upgrade. In this work, a series of novel GrO@MIL-53(Cr) composites were prepared from GrO and MIL-53(Cr). Their adsorptive performance for CO2/CH4 separation was experimentally investigated. IAST was applied to predict their adsorptive selectivity for CO2/CH4 separation. Results show that a small amount of GrO doping (1%) could significantly improve surface area and pore volume of the resulting 1GrO@MIL-53(Cr), while a remarkably enhanced CO2 uptake was observed with sufficient GrO doping (10%) for 10GrO@MIL-53(Cr) at 5bar and room temperature, which is 62% higher than that of its parental MIL-53(Cr). XRD indicates a quenched “breathing effect” could be responsible for the remarkably enhanced CO2 uptake. With this quenched breathing effect, 10GrO@MIL-53(Cr) shows a 16 times higher CO2/CH4 selectivity at 5bar for the equimolar CO2/CH4 mixture. SEM and TEM show well-defined compositing structures, while IR, Raman and TG suggest GrO@MIL-53(Cr) composites manage to preserve most of the crystallographic and chemical characteristics of their parent MIL-53(Cr).
      Graphical abstract image

      PubDate: 2017-04-17T16:52:05Z
       
  • Study of the foaming mechanisms associated with gas counter pressure and
           mold opening using the pressure profiles
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): John W.S. Lee, Richard E. Lee, Jing Wang, Peter U. Jung, Chul B. Park
      We investigated the foaming mechanisms associated with the gas counter pressure (GCP) and mold-opening processes during foam injection molding for products with high quality surface. The molding process involved injecting a polymer/nitrogen solution into a nitrogen-pressurized mold cavity. The preloaded cavity pressure (that is, the GCP) prevented cell nucleation and growth within the polymer melt. This was the case until the GCP was released (without opening the mold) or until the melt filled the mold cavity completely. Then the cavity thickness was suddenly increased by opening the mold. In an attempt to understand the mechanism of cell nucleation and growth, we monitored the pressure profile at several locations in the mold cavity during the molding process. We found that the pressure history in the mold cavity, both as a function of space and time, was the dominant factor that determined cell morphology. By applying the GCP and the mold-opening process, the cell size uniformity was improved when compared with conventional foam injection molding. These methods did not compromise the achievable void fraction. Using GCP and the mold-opening process also significantly improved the surface qualities of the foamed parts. This was because the premature cell growth at the flow front during the mold filling stage had been eliminated.

      PubDate: 2017-04-17T16:52:05Z
       
  • Impact of column material on electrostatics and entrainment of particles
           from gas-solid fluidized beds
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Farzam Fotovat, Kareena Gill, John R. Grace, Xiaotao T. Bi
      To investigate the impact of the column wall material on entrainment and electrification of fines in the freeboard of fluidized beds, fine powders were entrained by air at atmospheric temperature and 205kPa in columns of diameter 0.15m made of stainless steel and acrylic. Under equivalent operating conditions, changing the column wall material changed the entrainment flux and charge density of powders sampled from the freeboards of the columns. For all fines tested, the entrainment was lower for a column in which particles had a higher charge density. Depending on the work function of the fine particles and column wall material, increasing the gas velocity in the column could result in an increase or a decrease in the charge density of particles in the freeboard. Regardless of the impact of the column wall material on the particle charge density at different relative humidities (RH), the charge density of the fines decreased for dielectric particles and increased for conductive particles with increasing relative humidity.

      PubDate: 2017-04-17T16:52:05Z
       
  • Compaction of food powders: The influence of material properties and
           process parameters on product structure, strength, and dissolution
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): W. Robert Mitchell, Laurent Forny, Tim Althaus, Daniel Dopfer, Gerhard Niederreiter, Stefan Palzer
      During pressure agglomeration of food powders, it is often difficult to control the final product properties due to their complex material behaviours. The current study aims to better elucidate how the quality of a compact is impacted by the material characteristics of the raw materials as well as the process conditions applied. An amorphous powder was compacted under various conditions to investigate the influence of material properties, such as water activity and molecular weight, and process parameters (pressure and dwell time) on tablet porosity, tensile strength, and dissolution time. With increasing pressure, the porosity decreased and the strength increased, due to the formation of bridges between particles at their contact points. If the glass transition temperature (T g) was low (due to moisture-induced plasticisation or more extensive enzyme hydrolysis) and the compaction pressure high, then the temperature of the powder surpassed its T g; resulting in local occurrences of temporary glass transition within the powder bed, allowing for enhanced deformation and microsintering between particles. This led to stronger interparticle bridges and overall tablet crushing strength – this strength increase was particularly strong for longer dwell times, as the extent of microsintering was augmented. Tablets dissolved more quickly at higher water temperatures, but more slowly for higher compaction pressures – this may be explained by a change of dissolution regimes (erosion vs. disintegration). A higher molecular weight resulted in slower dissolution due to slower liquid penetration due to wetting, viscosity-building, and pore collapsing effects. The current work could be used to optimise the processing parameters, leading to improved product properties, particularly mechanical strength and reconstitution performance.
      Graphical abstract image

      PubDate: 2017-04-10T05:44:39Z
       
  • Effect of drying method on agglomeration degree of crystalline products
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Lisa-Marie Terdenge, Kerstin Wohlgemuth
      In crystallization a high effort for optimization and process control is made to produce crystalline batches with required specifications, like purity or crystal size distribution (CSD). However, the final product is affected by solid-liquid separation and drying also so that for an efficient process optimization all unit operations have to be considered. Especially if a high temperature dependency of solubility exists, a special attention should be paid to the drying process. Previous studies show that classical static drying is not the best choice in this case, since long contact time between crystals lead to uncontrolled agglomeration. This event need not necessarily result in different characteristics of the crystal size distribution (CSD), but reduced purity. Therefore we investigate systematically two different drying methods – fluid bed and rotary tube drying – concerning behavior of CSD and agglomeration degree in dependence of drying parameters used. Additionally we show that with the aid of the so-called agglomeration degree distribution, which we developed before, a deeper understanding of crystal agglomeration within the CSD is gained. As model system l-alanine/water is used. The results show that the product quality designed by cooling crystallization cannot be entirely maintained, but the formation of agglomerates is reduced in case of both methods.

      PubDate: 2017-04-10T05:44:39Z
       
  • Influence of solvothermal synthesis on the photocatalytic degradation
           activity of carbon nitride under visible light irradiation
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Che-Chia Hu, Mao-Sheng Wang, Wei-Zeng Hung
      The demand for the development of metal-free, visible-light-active photocatalysts is increasing. This study reports the solvothermal synthesis of carbon nitride (C3N4) photocatalysts by using acetonitrile as a solvent and solvothermal temperatures of 150–220°C. The crystalline structures of the resulting C3N4 samples were obtained following a conversion from a mixed pseudocubic/beta phase to a graphitic phase by increasing the solvothermal temperature and the filling fraction of the autoclave. The interlayer spacing of tri-s-triazine units in the (100) direction within graphitic C3N4 (g-C3N4) was obtained from X-ray diffraction measurements and was observed to decrease because of pressurization, leading to improved interlayer stacking of the tri-s-triazine units and a high degree of overlap between the n states and antibonding π orbitals. The prepared catalysts had band gap energies of 1.5–2.5eV, and the g-C3N4 samples had high photocatalytic activity during the degradation of methyl orange solutions under visible light irradiation. The g-C3N4 samples obtained at high temperatures and filling fractions exhibited lower photoluminescence emission intensities than did the C3N4 specimens with mixed phases (i.e., pseudocubic- and beta-C3N4), suggesting that these active g-C3N4 catalysts with compact planar tri-s-triazine units had efficient charge separation. The present study demonstrated the influence of the experimental conditions used in the synthesis of C3N4 on the subsequent photocatalytic degradation activity of the specimens under visible light irradiation.
      Graphical abstract image

      PubDate: 2017-04-03T10:09:22Z
       
  • Applications of Polynomial Chaos Expansions in optimization and control of
           bioreactors based on dynamic metabolic flux balance models
    • Abstract: Publication date: 10 August 2017
      Source:Chemical Engineering Science, Volume 167
      Author(s): Divya Kumar, Hector Budman
      This work proposes model based approaches for on-line or off-line economic optimization of batch reactors in the presence of model error (uncertainty). Polynomial Chaos Expansions are used as an effective and computationally efficient tool to propagate the error in model parameters into the optimizations’ cost functions. The computational efficiency of the proposed uncertainty propagation approach is essential for the implementation of the on-line approach that takes into account feedback corrections. The role of feedback, as applied in the on-line formulation, is proved to be instrumental for reducing conservatism of the optimization results. The proposed approaches can serve to design recipes for maximizing productivity in batch, fed-batch or perfusion operation of bioreactors.

      PubDate: 2017-04-03T10:09:22Z
       
 
 
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